When a speech/audio signal is transmitted in a packet communication system typified by Internet communication, a mobile communication system, or the like, compression/encoding technology is often used in order to increase speech/audio signal transmission efficiency. Also, there has been a growing need in recent years for a technology for encoding a wider-band speech/audio signal as opposed to simply encoding a speech/audio signal at a low bit rate.
In response to this need, various technologies have been developed for encoding a wideband speech/audio signal without increasing the post-encoding information amount. For example, Non-patent Document 1 presents a method whereby an input signal is transformed to a frequency-domain component, a parameter is calculated that generates high-band spectrum data from low-band spectrum data using a correlation between low-band spectrum data and high-band spectrum data, and band enhancement is performed using that parameter at the time of decoding.
Non-patent Document 1: Masahiro Oshikiri, Hiroyuki Ehara, Koji Yoshida, “Improvement of the super-wideband scalable coder using pitch filtering based spectrum coding”, Annual Meeting of Acoustic Society of Japan 2-4-13, pp. 297-298, September 2004